The best of the present day pressurized aircraft door systems employ over-center hooks as the locking elements. Such hooks are pivoted on an eccentric shaft. When the hook has engaged a pin the eccentric shaft is rotated which causes the hook to pull the door closed. When the shaft has rotated fully, the line between the hook pivot point and the pin center has passed the center of the eccentric shaft. Under ideal conditions, tension loads on the hook try to rotate the eccentric shaft in the locking direction. Frequently, however, small errors in rigging the eccentric shaft allow one or more of the hooks to stop prior to going over-center. Under these conditions, tension loads on the hook tend to unlock the system. These slight variations in position from locked to unlocked may not be visually obvious. Catastrophic failures have occurred due to unlocking under load in this manner.